1. Field of the Invention
This invention relates to a controlling device for automatically opening and closing a door of an automatic door system.
2. Description of the Prior Art
A controlling device for an automatic door is already known which comprises a human body detecting sensor such as a mat switch, and a controller responsive to a human body detection signal from the human body detecting sensor for developing forward and reverse rotation signals to a door driving motor, whereby a door is opened in response to a human body detection signal and is then closed after lapse of a predetermined period of time.
Such a human body detecting sensor develops a human body detection signal when a person comes within a predetermined detection area thereof. Thus, if a person comes within the detection area while the door is being closed, a human body detection signal is delivered to the controller so that rotation of the motor is reversed to open the door, that is, a turnover operation of the door is effected. However, there is a considerable time lag before the door is opened sufficiently to allow passage of the person. Accordingly, the person may be prevented from passing the door smoothly or be frightened at the door, or sometimes the person may accidentally collide with the door.
In order to resolve such a problem described above, it is only necessary to raise the speed of the turnover operation as high as possible or to increase or widen the detection area of the human body detecting sensor. However, if the speed of the turnover operation rises, an excessive force may be applied to a door driving mechanism and knocking of the door may occur, resulting in deterioration in durability of the door and in production of noises. This is particularly remarkable with a heavy door such as a door in which reinforced glass is used because its kinetic energy is high. Therefore, there is a limitation to an increase of the speed of a turnover operation of a door.
Meanwhile, if the detection area is too wide, then even a passenger who will only pass by the door and not pass the door may be detected, and hence the door may be opened or closed in vain.